mmallo
04-16-2017, 10:24 AM
This boat is a 1997 Supra Vision with the GM 5.7L GT-40 PCM EFI HO motor.
Case 1 (usually happens in a cold engine scenario):
Boat starts in high idle 1200 RPM and stays there - when put in gear, idle drops to 1K RPMs. Boat runs fine in this condition on the open water, easily goes 30 MPH shows no signs of any issues - no stalling.
Case 2 (usually happens in a warm engine scenario):
Boat starts in normal idle 650 RPM and runs fine in or out of gear. Easily goes 30 MPH on open water for hours. When idling back through the channel boat stalls out. Much harder to start - sometimes have to apply 3/4 throttle (out of gear) to get it to restart, and goes 10-15 seconds then dies again. Can repeat this cycle and stays running less each time. When in this condition after stalls, the oil light comes on and we hear the fuel control cell priming 4-5 times.
Spent a day troubleshooting (without a ton of tools):
Sanded and tightened all electrical to the batteries and the engine block/starter.
Pulled out and cleaned contacts to all the sensors on the throttle body.
Went to auto store and replaced the throttle position sensor as it looked worn and was indicated on the forums as a potential problem - however this had no effect.
Could not find an IAC (idle air control) like the ford engines have on the diagram - is there not one for the GM?
I have the engine diagrams from PCM - but just don't know where to go next. Looking for some advice here - should I just start swapping parts (low pressure pump, relays, more sensors?) or buy some diagnostic tools to get to the next step? (fuel pressure sensor, timing light, gm fault code reader)?
Case 1 (usually happens in a cold engine scenario):
Boat starts in high idle 1200 RPM and stays there - when put in gear, idle drops to 1K RPMs. Boat runs fine in this condition on the open water, easily goes 30 MPH shows no signs of any issues - no stalling.
Case 2 (usually happens in a warm engine scenario):
Boat starts in normal idle 650 RPM and runs fine in or out of gear. Easily goes 30 MPH on open water for hours. When idling back through the channel boat stalls out. Much harder to start - sometimes have to apply 3/4 throttle (out of gear) to get it to restart, and goes 10-15 seconds then dies again. Can repeat this cycle and stays running less each time. When in this condition after stalls, the oil light comes on and we hear the fuel control cell priming 4-5 times.
Spent a day troubleshooting (without a ton of tools):
Sanded and tightened all electrical to the batteries and the engine block/starter.
Pulled out and cleaned contacts to all the sensors on the throttle body.
Went to auto store and replaced the throttle position sensor as it looked worn and was indicated on the forums as a potential problem - however this had no effect.
Could not find an IAC (idle air control) like the ford engines have on the diagram - is there not one for the GM?
I have the engine diagrams from PCM - but just don't know where to go next. Looking for some advice here - should I just start swapping parts (low pressure pump, relays, more sensors?) or buy some diagnostic tools to get to the next step? (fuel pressure sensor, timing light, gm fault code reader)?